I love luggage debates, and have read many of them over the years. I have been accused of being a luggage collector and must confess I have acquired a ridiculous number of suitcases and bags of various styles and sizes. Agree with many of the opinions so far, and also agree it is a very individual matter. I am old enough to still recall the novelty of being able to buy extra clip-on wheels for a suitcase (bad idea - 1 came off in transit, leaving the bag with a terrible wobble), and my first hard-sided Samsonite Oyster whose wheels were destroyed by London cobblestones. I try and travel cabin-bag-only for up to a week, and must have at least 8 or 9 different cabin bags right now. However, as my mobility and hand-strength have now deteriorated, there are some definite factors in my luggage choices.
1. As light weight as possible, as I have difficulty lifting even the 7 kg max into the overhead lockers. My Cosmolite 20", as others have noted with delight, is 2.2 kg empty.
2. For me, wheels are essential. I agree that 2 wheels have many advantages over 4 for certain situations (control on slopes, rough surfaces etc), but I now prefer 4 wheels as it does not put the same strain on my wrist and I can even use the top of the handle as a support while walking it upright.
3. An external zip pocket large enough to take my 11" Mac Air for security screening access would make my Cosmolite ideal, but it lacks this feature. (Others of my soft-sided wheeled bags have such a pocket and it eases the struggle through security).
4. Being able to put my heavy handbag (which has a zip-open luggage sleeve) over the handles of the suitcase is another plus (which my uni-pole Cosmolite lacks, but others of my collection have this nice feature).
Price-wise I have spent from $50 to $400 on cabin bags over the years, and the price has frequently (but not always) reflected the quality and longevity. My vast

D) collection enables me to lend something slightly better than the orange corpse-bag mentioned by the OP to various friends and relatives, and it is often their less-careful handling of the bags which reveal the deficiencies - I suspect I am gentler than the average with my belongings. And a bit sentimental about some of the prettier ones (a lovely turquoise set of Samsonites is a particular sentimental favourite, but the cabin bag is international size and quite heavy empty, and the no-wheel duffle bag has lots of lovely zipped compartments, but - you guessed it - no wheels! No good for me any more except for car trips

).